Search for collectivity with azimuthal J/ψ-hadron correlations in high multiplicity p–Pb collisions at √sNN = 5.02 and 8.16 TeV

Abstract

We present a measurement of azimuthal correlations between inclusive J/ψand charged hadrons in p–Pbcollisions recorded with the ALICE detector at the CERN LHC. The J/ψare reconstructed at forward (p-going, 2.03 < y < 3.53) and backward (Pb-going, −4.46 < y < − 2.96) rapidity via their μ+μ−decay channel, while the charged hadrons are reconstructed at mid-rapidity (|η| <1.8). The correlations are ex-pressed in terms of associated charged-hadron yields per J/ψtrigger. Arapidity gap of at least 1.5 units is required between the trigger J/ψand the associated charged hadrons. Possible correlations due to collec-tive effects are assessed by subtracting the associated per-trigger yields in the low-multiplicity collisions from those in the high-multiplicity collisions. After the subtraction, we observe a strong indication of re-maining symmetric structures at _ϕ≈0and _ϕ≈π, similar to those previously found in two-particle correlations at middle and forward rapidity. The corresponding second-order Fourier coefficient (v2) in the transverse momentum interval between 3 and 6GeV/cis found to be positive with a significance of about 5σ. The obtained results are similar to the J/ψv2coefficients measured in Pb–Pb collisions at √sNN = 5.02TeV, suggesting a common mechanism at the origin of the J/ψv2.